Cytogenetic characterization of a colon adenocarcinoma from a familial polyposis coli patient

Chromosomal and methylation alterations in sporadic and familial adenomatous polyposis-related duodenal carcinomas

Primary carcinomas of the small intestine are rare and the mechanism of their pathogenesis is poorly understood. Patients with familial adenomatous polyposis (FAP) have a high risk of developing duodenal carcinomas. The aim of this study is to gain more insight into the development of duodenal carcinomas. Therefore, five FAP-related duodenal carcinomas were characterized for chromosomal and methylation alterations, which were compared to those observed in sporadic duodenal carcinomas. Comparative genomic hybridization (CGH) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) was performed in 10 primary sporadic and five primary FAP-related duodenal carcinomas. In the FAP-related carcinomas, frequent gains were observed on chromosomes 8, 17 and 19, whereas in sporadic carcinomas they occurred on chromosomes 8, 12, 13 and 20. In 60% of the sporadic carcinomas, gains in the regions of chromosome 12 were observed which were absent in the FAP-related carcinomas (P=0.04). Hypermethylation was observed in the immunoglobulin superfamily genes member 4 (IGSF4), TIMP metallopeptidase inhibitor 3 (TIMP3), Estrogen receptor 1 (ESR1), adenomatous polyposis coli (APC), H-cadherin (CDH13) and paired box gene 6 (PAX6) genes. Hypermethylation of PAX6 was only observed in FAP-related carcinomas (3/5) and not in sporadic carcinomas (P=0.02). In conclusion, in contrast to sporadic duodenal carcinomas, gains on chromosome 12 were not observed in duodenal carcinomas of patients with FAP. Identification of the genes in these regions of chromosome 12 could lead to a better understanding of the carcinogenesis pathways leading to sporadic and FAP-related duodenal carcinomas. Furthermore, hypermethylation seems to be a general feature of both FAP-related duodenal carcinomas as well as sporadic duodenal carcinomas with the exception of the PAX6 gene, which is methylated only in FAP-related carcinomas.

Chromosome number distribution and cellular DNA content in colorectal adenomas from polyposis and nonpolyposis patients

Ploidy analyses of colorectal adenomas were performed by combined flow cytometric DNA analysis of unfixed isolated nuclei and direct chromosome preparation after Colcemid incubation for 9-20 hours. Ten of 18 adenomas from nonpolyposis patients and 4 of 13 adenomas from patients with familial adenomatous polyposis yielded a mean of 25 countable metaphases (range 7-44) per tumor. Of 343 metaphases, only 38% had 46 chromosomes, and 62% were nondiploid. All but one adenoma had diploid or peridiploid modes in the range of 46-50 chromosomes. One adenoma was hyperploid, with a mode of 74 chromosomes and a correspondingly increased nuclear DNA content. In another two adenomas, the DNA analyses showed small hyperploid populations constituting 6% and 2% of the cells. The most striking difference between the DNA analyses and chromosome number distributions was that 13% of all metaphases were hyperploid with chromosome numbers outside the perimodal range but, except in one adenoma, without indication in the DNA histogram of corresponding hyperploid cell populations. We propose that these aberrant metaphases indicate an early acquired genetic instability of the neoplastic epithelium, which may be instrumental in generation of hyperploid, invasive clones, which constitute most colorectal carcinomas.

Numerical chromosome changes in 165 malignant tumors. Evidence for a nonrandom distribution of normal chromosomes

The numbers of normal copies of each of the chromosomes in representative karyotypes from 165 malignant tumors of the bladder, breast, cervix, colorectum, and testis studied in this laboratory or described in the literature were assessed to determine whether particular chromosomes were over- or underrepresented. For each chromosome, the mean number of copies was expressed as a percentage of the number expected on the basis of the total number of chromosomes in the karyotypes. The most highly represented autosomes in the tumors as a whole were, in descending order of frequency, numbers 7, 20, 12, 19, 21, and 3, while those most underrepresented were numbers 10, 1, 4, 5, 14, 17, 11, and 18. In tumors of males, the Y tended to be underrepresented. The X was highly represented in the testicular tumors (there were usually two or more copies) and in colorectal tumors of males, but not in the other tumor categories studied. For the tumors as a whole, statistically significant differences could be demonstrated between pairs of autosomes that were at opposite ends of the frequency range. Differences between tumors at the different sites studied were not demonstrable. It is suggested that the determination of the number of normal copies of chromosomes, i.e., whether there are more or fewer than expected, may usefully complement observations on structural changes by reflecting the presence of oncogenes and tumor-suppressor genes, respectively. It may also point to chromosomes that are involved in significant genic changes in which cytogenetic observations on structural changes are equivocal.